JP2004355701A - Optical disk, and its manufacturing method and device - Google Patents

Optical disk, and its manufacturing method and device Download PDF

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Publication number
JP2004355701A
JP2004355701A JP2003150978A JP2003150978A JP2004355701A JP 2004355701 A JP2004355701 A JP 2004355701A JP 2003150978 A JP2003150978 A JP 2003150978A JP 2003150978 A JP2003150978 A JP 2003150978A JP 2004355701 A JP2004355701 A JP 2004355701A
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Prior art keywords
film
substrate
layer
semi
transmissive
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Japanese (ja)
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Yasuaki Odera
泰章 大寺
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Toshiba Corp
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Toshiba Corp
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Priority to JP2003150978A priority Critical patent/JP2004355701A/en
Priority to US10/804,100 priority patent/US20040241575A1/en
Priority to CN200410030498.2A priority patent/CN1573988A/en
Publication of JP2004355701A publication Critical patent/JP2004355701A/en
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/2403—Layers; Shape, structure or physical properties thereof
    • G11B7/24035—Recording layers
    • G11B7/24038—Multiple laminated recording layers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/257—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers
    • G11B7/2578—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/258—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of reflective layers
    • G11B7/2585—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of reflective layers based on aluminium
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/257—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers
    • G11B2007/25705—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials
    • G11B2007/25706—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials containing transition metal elements (Zn, Fe, Co, Ni, Pt)
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/253—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates
    • G11B7/2531—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates comprising glass
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/253—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates
    • G11B7/2533—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates comprising resins
    • G11B7/2534—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates comprising resins polycarbonates [PC]
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/256—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers improving adhesion between layers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/26—Apparatus or processes specially adapted for the manufacture of record carriers

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Optical Record Carriers And Manufacture Thereof (AREA)
  • Manufacturing Optical Record Carriers (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a two-layer disk wherein reflectances of both layers are equal to each other for a blue laser and a small pit is not buried either. <P>SOLUTION: The read only single-sided two layer optical disk is provided with a first substrate 15 having pits showing information formed on one surface thereof and a reflection film 14 on the pit side surface and a second light transmissive substrate 11 having pits showing information formed on one surface thereof and a semitransmissive film 12 consisting of silver or a silver alloy consisting essentially of silver on the pit side surface. The reflection film 14 and the semitransmissive film 12 are provided opposite to each other and the part between the reflection film and the semitransmissive film is filled up with an intermediate layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は情報記録層を２層有し、該情報をディスクの一方の側からレーザ光により読取る再生専用片面２層光ディスクに関する。
【０００２】
【従来の技術】
光ディスク大容量化の手段の一つとして２層化がある。特にＤＶＤ−ＲＯＭなど再生専用ディスクでは、その構造および製造法が簡便なことから、片面２層ディスクが一般的に生産され使用されている。
【０００３】
片面２層ディスクは、情報を再生する光ピックアップヘッド側から見て、手前の層の反射膜が半透明膜である必要があるが、現在使用されている金（Ａｕ）やシリコン（Ｓｉ）はＤＶＤの赤色レーザに対しては半透明膜として働くが、次世代ＤＶＤの青色レーザに対してはその反射率が高過ぎたり低過ぎたりして好ましくない。
【０００４】
そこで下記特許文献１で示される従来技術では、１層目２層目の反射膜それぞれに金属膜に加え硫化亜鉛（ＺｎＳ）の膜を積層することで、青色レーザに対して両層からの反射光量が等しくなる２層ディスクを実現している。しかしこの構造で作られた反射膜で反射光量を調整すると、その膜厚が６０〜８０ｎｍ程度にもなってしまう。
【０００５】
ところが次世代ディスクのピットは、深さは７０ｎｍでピット幅は２５０ｎｍ程度しかないため、特にピットが凹となるＬ１（奥側）層側では層厚を更に薄くしないと最短ピットが埋まって再生信号特性が悪化してしまう問題がある。
【０００６】
【特許文献１】
特開平９−２９３２７０
【０００７】
【発明が解決しようとする課題】
上記したように、青色レーザに対して両層からの反射光量が等しくなる２層ディスクを実現するために、金属膜に誘電体層を積層した反射膜を用いた場合、該反射膜はその膜厚が６０〜８０ｎｍ程度にもなってしまい、ピットが凹となるＬ１（奥側）層側ではピットが埋まって再生信号特性が悪化するという問題が生じる。
【０００８】
従って本発明は青色レーザに対して両層の反射率が等しく、かつ小さなピットも埋まらない２層ディスクを製作するを目的とする。
【０００９】
【課題を解決するための手段】
上記目的を達成するために本発明の一実施形態に係る光ディスクは、情報を示す第１のピットが片面に形成され、該ピット側表面に反射膜を有する第１の基板と、情報を示す第１とは異なる第２のピットが片面に形成され、該ピット側表面に銀又は銀を主成分とする銀合金からなる半透過膜を有する光透過性の第２の基板と、中間層とを具備し、前記反射膜及び半透過膜は対向して設けられ、該反射膜及び半透過膜の間は光透過性の前記中間層で充填されている。
【００１０】
光ピックアップヘッドから見て手前の層（Ｌ０層）に膜厚１５ｎｍ程度の銀（若しくはその合金）を半透過膜として、奥側の層（Ｌ１層）に膜厚２５ｎｍ程度のアルミニウムを反射膜として使用する。このように薄い膜を用いることで、青色レーザに対して両層の反射率が等しく、かつ小さなピットも埋まらない再生専用片面２層光ディスクが実現できる。
【００１１】
手前の膜に例えばアルミなどの反射率の比較的高い膜を用いるとその最適膜厚が５ｎｍ程度と薄くなりすぎてしまい、安定して成膜出来ないうえに膜の耐久性にも問題がある。そのため本発明では、Ｌ０層の膜としては銀を用いて膜厚を１５ｎｍ程度まで厚くして、安定して生産できるようにした。
【００１２】
更に、従来例のように誘電体層を設けずに、本発明では金属層のみによりＬ０層及びＬ１層を構成するので、成膜レートが高く生産効率が上がる。
【００１３】
【発明の実施の形態】
以下、図面を参照しながら本発明の実施の形態について詳細に説明する。
【００１４】
図１は本発明に係る２層光ディスクの断面図、図２は本発明に係る光ディスク製造方法の流れ図、図３は本発明の構造による２層光ディスクの再生波形である。
【００１５】
２層光ディスクは通常、図１のような構造を有し、光が入射する側の層（Ｌａｙｅｒ０）として半透過膜１２、奥側の層（Ｌａｙｅｒ１）として全反射膜１４が成膜されている。信号パターン（情報）はポリカーボネートなどの樹脂で成形された基板１１、１５上にピットとして転写されており、２枚の成形基板１１、１５は紫外線硬化樹脂などからなる中間層１３を介して貼り合わされている。基板１１及び１５上には一般に異なる情報が記録されるので、当然、基板１１上のピット配列と基板１５上のピット配列は異なる。
【００１６】
本実施形態では、ディスクは直径１２０ｍｍ、厚さ１．２ｍｍ（０．６ｍｍの基板２枚の貼り合せ）であり、かつ再生専用のＲＯＭディスクであるとする。しかし、本発明はこの実施形態に限定されるものではなく、１．１ｍｍの基板に０．１ｍｍの透明カバー層をつけた２層光ディスクなどでも適用できる。又、再生光については波長４００ｎｍ程度の青色光で、記録パターンのピット形状は深さ７０ｎｍ、幅が２５０ｎｍとし、中間層の厚さは２０μｍとする。しかしこれについてももちろんこの形態に限られるわけではなく、赤色光もしくはその他の波長の光で情報を再生するディスクでも良く、記録パターンはもっと微細なものでも良いし、中間層は例えば１５μｍや２５μｍ程度でも良い。
【００１７】
このような２層光ディスクの作成方法を図２に沿って以下に述べる。先ず、原盤としては表面を研磨洗浄したガラス（もしくはシリコン）基板３１を用いる（ＳＴ０１）。この原盤表面にフォトレジスト３２を塗布し（ＳＴ０２）、その表面をレーザー光や電子ビームで露光することで情報を記録する（ＳＴ０３）。次に露光した原盤を現像しピットの凹凸を形成する（ＳＴ０４）。その原盤をメッキ処理することでスタンパ（一般にはニッケル）３３を作製する（ＳＴ０５）。そのスタンパ３３を型として射出成形により樹脂（一般にはポリカーボネート）成形板１１を作製する（ＳＴ０６）。
【００１８】
この際、上述の方法でＬａｙｅｒ０とＬａｙｅｒ１の記録パターンをもつ成形基板を２枚準備する。その成形板のＬａｙｅｒ０の方に半透過膜１２をＬａｙｅｒ１の方に全反射膜１４をマグネトロンスパッタ等の方法で成膜する（ＳＴ０７）。その後、その２枚の成形板を所定厚の紫外線硬化型接着剤などを用いて貼り合せて（ＳＴ０８）、２層光ディスクの完成となる。紫外線硬化型接着剤の層は中間層１３となる。
【００１９】
従来のＤＶＤなどの赤色光で再生する光ディスクでは、工程ＳＴ０７で用いる反射膜として金（Ａｕ）やシリコン（Ｓｉもしくはその化合物）が用いられていた。しかし、これらの膜は青色光に対する反射率が高すぎたり低過ぎたりするため、次世代光ディスクの半透過膜としては適していない。このため、例えば上記特開平９−２９３２７０号公報などでは半透過膜および全反射膜を金属膜と誘電体膜（例えば硫化亜鉛：ＺｎＳ）の積層構造にして、青色光に対する反射率を調整している。
【００２０】
しかしその方法で反射率を調整した場合、膜の総厚は６０から８０ｎｍとなるため次世代光ディスクの小さなピットに対しては適用できない。なぜならば、次世代光ディスクはそのピット寸法が深さ７０ｎｍ程度、幅２５０ｎｍ程度であるため、厚さ６０から８０ｎｍの膜を成膜した場合に特にピットが凹状で膜の上から光で読むことになるＬａｙｅｒ１側については、最小ピット等が膜で埋まってしまい大幅に再生信号が劣化するからである。
【００２１】
このため、青色光で再生する次世代の高密度光ディスクについては、Ｌａｙｅｒ１側の全反射膜をなるべく薄くしたい。量産に使用可能な膜のなかでは例えばアルミニウム（Ａｌ）などが向いている。しかし、Ａｌは半透過膜に用いる場合その最適膜厚が５ｎｍ程度とあまりに薄く、又その成膜レートも極端に高速なため安定して正確な膜厚制御を行うことが困難である。膜厚のばらつきは反射率のばらつきとなってしまい好ましくない。そこで半透過膜の方は、銀（Ａｇ）を用いることにより安定した成膜を可能とした。
【００２２】
本実施形態では、Ｌａｙｅｒ１の全反射膜として膜厚２０から４０ｎｍのＡｌを、Ｌａｙｅｒ０の半透過膜として膜厚１０から３０ｎｍのＡｇを使用する。こうすれば両層からの反射光量が等しく調整され、ピットが膜に埋まることなく良好な再生波形が得られる。このときＬａｙｅｒ０の青色レーザ光に対する反射率は１８から３２％であり、次世代ＤＶＤとして好適な値である。なおＡｇについては耐腐食性の目的で光学特性が変わらない程度の微量の添加物（例えばパナジウム（Ｐｄ）や銅（Ｃｕ））を混ぜ、銀合金にしても構わない。更に生産性等を考慮しなければＬａｙｅｒ０として、ニッケル又はニッケル合金、クロム又はクロム合金、あるいはニッケルクロム合金を使用できる。
【００２３】
Ｌａｙｅｒ０の半透過膜として銀合金１７ｎｍを、Ｌａｙｅｒ１の全反射膜としてアルミニウム２５ｎｍをそれぞれ成膜した１５ＧＢ／層密度の２層光ディスクの再生波形を図３に示す。両層からの再生信号強度はほぼ等しく、良好な品質の再生波形が得られている。
【００２４】
本発明による光ディスクの構造は、従来のように反射率調整にＺｎＳ等の誘電体を用いる方法はとらず、金属膜のみを用いるために成膜レートも速く生産効率が良いという利点も持つ。
【００２５】
【発明の効果】
以上説明したように本発明によれば、青色レーザに対して両層の反射率が等しく、かつ小さなピットも埋まらない２層ディスクを製作することが出来る。
【図面の簡単な説明】
【図１】２層光ディスクの断面図。
【図２】光ディスク製造方法を示す流れ図。
【図３】本発明による２層光ディスクの再生波形図。
【符号の説明】
１１、１５…成形基板、１２…半透過膜、１３…中間層、１４…全反射膜、３１…ガラス基板、３２…フォトレジスト、３３…スタンパ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a read-only single-sided dual-layer optical disk having two information recording layers and reading the information from one side of the disk by a laser beam.
[0002]
[Prior art]
As one of means for increasing the capacity of an optical disc, there is a two-layer structure. In particular, for a read-only disc such as a DVD-ROM, a single-sided, dual-layer disc is generally produced and used because of its simple structure and simple manufacturing method.
[0003]
When viewed from the optical pickup head side for reproducing information, a single-sided dual-layer disc requires that the reflective film on the front layer be a translucent film, but gold (Au) and silicon (Si) currently used are not used. It works as a translucent film for the red laser of DVD, but its reflectance is too high or too low for the blue laser of the next generation DVD, which is not preferable.
[0004]
Therefore, in the prior art shown in Patent Document 1, by laminating a zinc sulfide (ZnS) film in addition to a metal film on each of the first and second reflective films, reflection from a blue laser from both layers is achieved. This realizes a two-layer disc with the same amount of light. However, if the amount of reflected light is adjusted by the reflective film made with this structure, the film thickness will be about 60 to 80 nm.
[0005]
However, the pits of the next-generation disc have a depth of only 70 nm and a pit width of only about 250 nm. In particular, on the L1 (rear side) layer side where the pits are concave, unless the layer thickness is further reduced, the shortest pits are buried and the reproduction signal There is a problem that characteristics are deteriorated.
[0006]
[Patent Document 1]
JP-A-9-293270
[0007]
[Problems to be solved by the invention]
As described above, in order to realize a two-layer disc in which the amount of light reflected from both layers with respect to the blue laser is equal, when a reflective film in which a dielectric layer is laminated on a metal film is used, the reflective film is the film. The thickness becomes about 60 to 80 nm, and there is a problem that the pits are buried on the L1 (rear side) layer side where the pits are concave, and the reproduction signal characteristics deteriorate.
[0008]
Accordingly, an object of the present invention is to produce a two-layer disc in which both layers have the same reflectance to a blue laser and do not fill even small pits.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, an optical disc according to one embodiment of the present invention has a first pit indicating information on one surface, a first substrate having a reflective film on the pit side surface, and a first pit indicating information. A second pit different from 1 is formed on one side, and a light-transmitting second substrate having a semi-transmissive film made of silver or a silver alloy containing silver as a main component on the pit side surface, and an intermediate layer. The reflective film and the semi-transmissive film are provided to face each other, and the space between the reflective film and the semi-transmissive film is filled with the light-transmitting intermediate layer.
[0010]
As a layer (L0 layer) in front of the optical pickup head, silver (or an alloy thereof) having a thickness of about 15 nm is used as a semi-transparent film, and aluminum (about 25 nm) is used as a reflective film in a layer (L1 layer) on the back side. use. By using such a thin film, it is possible to realize a read-only single-sided dual-layer optical disk in which the reflectance of both layers is equal to a blue laser and small pits are not filled.
[0011]
If a film having a relatively high reflectance, such as aluminum, is used as the film in the foreground, the optimum film thickness is too thin, about 5 nm, so that the film cannot be formed stably and there is a problem in the durability of the film. . Therefore, in the present invention, the thickness of the L0 layer film is increased to about 15 nm by using silver to enable stable production.
[0012]
Further, in the present invention, the L0 layer and the L1 layer are constituted only by the metal layer without providing the dielectric layer as in the conventional example, so that the film formation rate is high and the production efficiency is increased.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0014]
FIG. 1 is a sectional view of a two-layer optical disk according to the present invention, FIG. 2 is a flowchart of an optical disk manufacturing method according to the present invention, and FIG. 3 is a reproduction waveform of a two-layer optical disk according to the structure of the present invention.
[0015]
A two-layer optical disc usually has a structure as shown in FIG. 1, in which a semi-transmissive film 12 is formed as a layer on which light is incident (Layer 0), and a total reflection film 14 is formed as a layer on the back side (Layer 1). . The signal pattern (information) is transferred as pits on substrates 11 and 15 formed of a resin such as polycarbonate, and the two formed substrates 11 and 15 are bonded together via an intermediate layer 13 made of an ultraviolet curable resin or the like. ing. Since different information is generally recorded on the substrates 11 and 15, the pit arrangement on the substrate 11 and the pit arrangement on the substrate 15 are naturally different.
[0016]
In this embodiment, it is assumed that the disk is a ROM disk having a diameter of 120 mm and a thickness of 1.2 mm (two 0.6 mm substrates are bonded together), and is a read-only ROM disk. However, the present invention is not limited to this embodiment, and can be applied to a two-layer optical disk in which a 1.1 mm substrate is provided with a 0.1 mm transparent cover layer. The reproducing light is blue light having a wavelength of about 400 nm, the pit shape of the recording pattern is 70 nm in depth, the width is 250 nm, and the thickness of the intermediate layer is 20 μm. However, this is of course not limited to this mode, and a disc for reproducing information with red light or light of another wavelength may be used, the recording pattern may be finer, and the intermediate layer may be, for example, about 15 μm or 25 μm. But it's fine.
[0017]
A method for producing such a two-layer optical disc will be described below with reference to FIG. First, a glass (or silicon) substrate 31 whose surface is polished and cleaned is used as a master (ST01). A photoresist 32 is applied to the surface of the master (ST02), and information is recorded by exposing the surface to laser light or an electron beam (ST03). Next, the exposed master is developed to form pit irregularities (ST04). A stamper (generally nickel) 33 is produced by plating the master disc (ST05). Using the stamper 33 as a mold, a resin (generally polycarbonate) molded plate 11 is produced by injection molding (ST06).
[0018]
At this time, two molded substrates having the recording patterns of Layer 0 and Layer 1 are prepared by the method described above. The semi-transmissive film 12 is formed on Layer 0 of the formed plate, and the total reflection film 14 is formed on Layer 1 by a method such as magnetron sputtering (ST07). Thereafter, the two molded plates are bonded to each other using an ultraviolet-curable adhesive having a predetermined thickness (ST08), thereby completing a two-layer optical disk. The layer of the ultraviolet curable adhesive becomes the intermediate layer 13.
[0019]
In a conventional optical disc that reproduces with red light, such as a DVD, gold (Au) or silicon (Si or a compound thereof) is used as a reflective film used in step ST07. However, these films have too high or too low reflectance for blue light, and thus are not suitable as semi-transmissive films for next-generation optical disks. For this reason, for example, in the above-mentioned Japanese Patent Application Laid-Open No. 9-293270, the semi-transmissive film and the total reflection film have a laminated structure of a metal film and a dielectric film (for example, zinc sulfide: ZnS) to adjust the reflectance to blue light. I have.
[0020]
However, when the reflectance is adjusted by that method, the total thickness of the film is 60 to 80 nm, so that it cannot be applied to small pits of the next-generation optical disk. This is because the next-generation optical disc has a pit size of about 70 nm in depth and about 250 nm in width, and when a film having a thickness of 60 to 80 nm is formed, the pits are particularly concave and can be read with light from above the film. This is because, on the layer 1 side, the minimum pits and the like are buried in the film, and the reproduced signal is greatly deteriorated.
[0021]
For this reason, for a next-generation high-density optical disk that reproduces with blue light, it is desired to make the total reflection film on the Layer 1 side as thin as possible. Among films that can be used for mass production, for example, aluminum (Al) is suitable. However, when Al is used as a semi-transmissive film, its optimum film thickness is as extremely small as about 5 nm, and its film formation rate is extremely high, so that it is difficult to stably and accurately control the film thickness. Variations in film thickness result in variations in reflectance, which is not preferable. Therefore, the use of silver (Ag) for the semi-permeable film enables stable film formation.
[0022]
In the present embodiment, Al having a thickness of 20 to 40 nm is used as the total reflection film of Layer 1 and Ag of 10 to 30 nm is used as the semi-transmissive film of Layer 0. In this way, the amount of reflected light from both layers is adjusted equally, and a good reproduced waveform can be obtained without pits being buried in the film. At this time, the reflectance of Layer 0 with respect to the blue laser light is 18 to 32%, which is a value suitable for a next-generation DVD. Ag may be mixed with a small amount of additive (for example, vanadium (Pd) or copper (Cu)) to the extent that the optical characteristics do not change for the purpose of corrosion resistance, and may be made into a silver alloy. If productivity is not taken into consideration, nickel or a nickel alloy, chromium or a chromium alloy, or a nickel-chromium alloy can be used as Layer0.
[0023]
FIG. 3 shows a reproduction waveform of a 15 GB / layer density two-layer optical disc in which a silver alloy of 17 nm is formed as a semi-transmissive film of Layer 0 and an aluminum film of 25 nm is formed as a total reflection film of Layer 1. The reproduced signal intensities from both layers are almost equal, and a reproduced waveform of good quality is obtained.
[0024]
The structure of the optical disk according to the present invention has the advantage that the film formation rate is high and the production efficiency is good because only the metal film is used instead of the method using a dielectric such as ZnS for adjusting the reflectivity as in the related art.
[0025]
【The invention's effect】
As described above, according to the present invention, it is possible to manufacture a two-layer disc in which both layers have the same reflectance to a blue laser and do not fill even small pits.
[Brief description of the drawings]
FIG. 1 is a sectional view of a two-layer optical disc.
FIG. 2 is a flowchart showing an optical disk manufacturing method.
FIG. 3 is a reproduction waveform diagram of a two-layer optical disc according to the present invention.
[Explanation of symbols]
11, 15: molded substrate, 12: semi-permeable film, 13: intermediate layer, 14: total reflection film, 31: glass substrate, 32: photoresist, 33: stamper

Claims (8)

情報を示す第１のピットが片面に形成され、該ピット側表面に反射膜を有する第１の基板と、
情報を示す第１とは異なる第２のピットが片面に形成され、該ピット側表面に銀又は銀を主成分とする銀合金からなる半透過膜を有する光透過性の第２の基板と、中間層とを具備し、
前記反射膜及び半透過膜は対向して設けられ、該反射膜及び半透過膜の間は光透過性の前記中間層で充填されていることを特徴とする光ディスク。A first substrate having information on a first pit formed on one surface and having a reflective film on the pit side surface;
A light-transmissive second substrate having a second pit different from the first indicating information formed on one surface and having a semi-transmissive film made of silver or a silver alloy containing silver as a main component on the pit side surface; And an intermediate layer,
An optical disk, wherein the reflective film and the semi-transmissive film are provided to face each other, and the space between the reflective film and the semi-transmissive film is filled with the light-transmitting intermediate layer. 前記第１の基板の反射膜は、アルミニウムで形成されていることを特徴とする請求項１記載の光ディスク。The optical disc according to claim 1, wherein the reflection film of the first substrate is formed of aluminum. 前記第２の基板の前記半透過膜の膜厚は１０から３０ｎｍであることを特徴とする請求項１記載の光ディスク。2. The optical disk according to claim 1, wherein said semi-transmissive film of said second substrate has a thickness of 10 to 30 nm. 前記第１の基板の前記アルミニウムで形成される反射膜の膜厚は２０から４０ｎｍであることを特徴とする請求項１記載の光ディスク。2. The optical disk according to claim 1, wherein a thickness of the reflection film formed of aluminum on the first substrate is 20 to 40 nm. 情報を示すピットが形成された第１の成形基板上にアルミニウムの反射膜を成膜する工程と、
情報を示すピットが形成された光透過性の第２の成形基板上に銀又は銀を主成分とする銀合金の半透過膜を成膜する工程と、
前記反射膜及び半透過膜を対向させ、紫外線硬化型接着剤を用いて前記第１及び第２の成形基板を貼り合せる工程と、
を具備することを特徴とする光ディスク製造方法。Forming a reflective film of aluminum on the first molded substrate on which pits indicating information are formed;
Forming a semi-transparent film of silver or a silver alloy containing silver as a main component on a light-transmissive second molded substrate on which pits indicating information are formed;
A step of causing the reflective film and the semi-transmissive film to face each other, and bonding the first and second molded substrates together using an ultraviolet-curable adhesive;
An optical disk manufacturing method, comprising: 前記第１の基板の前記反射膜の膜厚は２０から４０ｎｍであることを特徴とする請求項５記載の光ディスク製造方法。6. The method according to claim 5, wherein the thickness of the reflection film of the first substrate is 20 to 40 nm. 前記第２の基板の前記半透過膜の膜厚は１０から３０ｎｍであることを特徴とする請求項５記載の光ディスク製造方法。6. The method according to claim 5, wherein the thickness of the semi-transmissive film of the second substrate is 10 to 30 nm. 情報を示すピットが形成された第１の成形基板上にアルミニウムの反射膜を成膜する手段と、
情報を示すピットが形成された光透過性の第２の成形基板上に銀又は銀を主成分とする銀合金の半透過膜を成膜する手段と、
前記反射膜及び半透過膜を対向させ、紫外線硬化型接着剤を用いて前記第１及び第２の成形基板を貼り合せる手段と、
を具備することを特徴とする光ディスク製造装置。Means for forming an aluminum reflective film on the first molded substrate on which pits indicating information are formed;
Means for forming a semi-permeable film of silver or a silver alloy containing silver as a main component on a light-transmissive second molded substrate on which pits indicating information are formed;
Means for causing the reflective film and the semi-transmissive film to face each other, and bonding the first and second molded substrates together using an ultraviolet-curable adhesive;
An optical disk manufacturing apparatus, comprising:
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